The goal of this Program Project is understanding the DNA sequence organization of the eukaryotic genome. It appears evident that the structural basis of gene regulation in higher organisms lies in the specific organization of genomic DNA sequences. Many of the individual research projects involve recombinant DNA clones. Most studies concern genomic sequence organization of sea urchin and Drosophila DNAs. The project is divided into four task areas, as follows: 1) Development of new technology and improvement of existing technology; 2) analysis of sequence organization in the vicinity of particular genes or genetic loci; 3) investigations concerned with the organization, character and evolution of repetitive sequences; and 4) miscellaneous sequence organization problems.